The invention relates to electronic memory and, more particularly, to an electronic circuit and method for storing and accessing data.
Electronic devices are often identically manufactured in large numbers in order to decrease their average cost. The resulting devices may be intended for different uses. In addition the manufacturing process may result in some variation in the parameters of devices. In both of those cases, non-volatile memory can be used to store information that differentiates the devices.
When electronic devices that are manufactured in an identical manner are intended for use in different applications, functionality may be built into the devices that is triggered by the presence or absence of data in non-volatile memory. In a simple example, an electronic device may be used in one of two products. A single non-volatile bit is programmed with either a high or low voltage. A high voltage would enable functionality appropriate to the first product, while a low voltage would enable functionality appropriate for the second product. A greater amount of non-volatile memory would allow for greater diversity of function.
When electronic devices that are manufactured in an identical manner are intended for use in the same application, non-volatile memory may still be useful for storing data that calibrates the device. For example, a particular manufacturing process could result in variations in electrical parameters. A circuit could be included in the electronic device that modifies those parameters in accordance to the data in a non-volatile memory. A post-manufacture test could be performed to indicate the electrical parameter for a particular device. The non-volatile memory could then be programmed so that the modification circuit corrects any deviation from the desired value of the electrical parameter.
Non-volatile memory is also useful for other tasks in electronic devices as is known to those of skill in the art. Non-volatile memory circuits and methods of using non-volatile memory have utility in the electronic device industry.
The present invention is directed to an electronic circuit with non-volatile memory, a method for accessing non-volatile memory, and systems employing the circuit or method.
In one embodiment of the electronic circuit with non-volatile memory of the present invention, the non-volatile memory includes several memory cells each of which has a voltage state as data. The non-volatile memory also includes an output. Connected to that output are the inputs of a plurality of latches. The latches can be read independently through their outputs. A refresh circuit is coupled to the address lines of the non-volatile memory and is also coupled to the write inputs of the latches. The data contained in the memory cells of the non-volatile memory is represented by the data contained in the latches.
In a more specific embodiment of the present invention, the non-volatile memory is EEPROM (electrically erasable programmable read-only memory). In another more specific embodiment of the invention, the circuit includes a timer that activates the refresh circuit at a specified frequency. In another more specific embodiment of the invention, the circuit includes a detector for each latch. The detectors monitor the data in the latches and generate a signal when the data changes. In response to the signal, the refresh circuit is activated.
In a method embodiment of the present invention, a non-volatile memory is programmed with a plurality of bits representing differentiation data. The differentiation data is sequentially output to a set of latches. At least two of the latches are simultaneously accessed for their copy of the differentiation data.
In another more specific method embodiment of the invention, the step of sequentially outputting the differentiation data to the latches occurs at power up. In another more specific embodiment of the invention, the contents of each latch are monitored. If a change in state is detected a signal is generated. In response to the signal, the differentiation data is sequentially output from the non-volatile memory. In another embodiment, the signal also halts a system. In more specific method embodiments of the invention, the differentiation data is calibration or configuration data.
A feature of the invention is accessing non-volatile memory in an electronic circuit.
Another feature is storing differentiation data in an electronic circuit.
Another feature is monitoring data integrity in an electronic circuit.
An advantage of the present invention is simultaneous access to multiple differentiation bits.
Another advantage is accurately maintained differentiation data.
Still another advantage is reduced circuit implementation area.
Another advantage is post-manufacture calibration.
Another advantage is post-manufacture configuration.
Other and further features and advantages will be apparent from the following description of presently preferred embodiments of the invention, given for the purpose of disclosure and taken in conjunction with the accompanying drawings. Not all embodiments of the invention will include all the specified advantages. For example, one embodiment may only accurately maintain differentiation data, while another only reduces circuit implementation area.